This invention relates to battery powered energy-using devices which operably distinguish between different types of battery power sources, and in particular pertains to safe means for charging rechargeable batteries built in to the energy-using device, while, in one aspect, also allowing the device to be powered by non-rechargeable (primary) batteries yet precluding recharging of the same.
Governmental legislation has recently come into force or is imminent in various European countries, as well as in certain states in the United States of America requiring that battery powered energy-using devices be constructed to provide easy access to the battery compartment. In this manner the batteries may be readily removed from the energy-using devices thereby allowing recycling of the device (minus the battery), as well as permitting collection of the batteries and possible reclaiming of the components thereof. Otherwise, the batteries, some of which contain toxic materials such as mercury or cadmium, may be deposited in landfills with the potential of creating an environmental hazard. An outgrowth of this legislation, whereby the battery compartment will now be easily accessible to the user of the device, and recognizing the growing tendency to utilize longer lasting rechargeable batteries in place of non-rechargeable primaries, is the risk that a battery may be installed or replaced in the device which is not compatible with its power system. For instance, a user may inadvertently replace a rechargeable battery with a primary battery in an AC/DC device such as a portable radio cassette tape player, resulting in recharging of the primary battery when the power cord is inserted into the AC outlet. This situation will likely lead to rupture or explosion of the battery, presenting a health hazard, or leakage of electrolyte which may ruin the energy-using device.
One attempt to overcome the foregoing problem involved the use of a special terminal extension carried by one of the power terminal contacts of the rechargeable battery, so that only the rechargeable battery could be charged in the circuit contained within the energy-using device (see U.S. Pat. No. 4,645,996 to Toops). A battery of non-standard size, of increased cost, had to be used.
In a related approach, certain manufacturers of portable radio cassette tape players and televisions have enclosed coupons with their devices which provides the purchaser with the option of sending away for a specially designed rechargeable battery pack to substitute for the plurality of primary batteries which normally come with the appliance. This special battery pack, examples of which are disclosed more fully in U.S. Pat. No. 4,489,286 to Beachy and U.S. Pat. No. 4,628,242 to Scholefield, employs an extended battery housing provided with an annular side charging ring adapted to mate with a custom charging terminal built in to the energy-using device. The design and placement of the charging terminal, and associated charging circuitry contained within the energy-using device, prevents the recharging of the primary battery installed in the compartment, while allowing recharging of the special rechargeable battery pack.
Not only is there a need for the energy-using device to be configured to distinguish between primary and rechargeable batteries, but also to discriminate between rechargeables which, because of their internal construction, may be designed for different rates of charge and/or discharge. For instance, some rechargeable nickel-cadmium batteries are designed for overnight charging (C/10 rate), others are capable of "quick" charge (three hour rate), and others are so-called "fast" charge capable (C rate, equivalent to a one hour rate). If a slow or quick charge type nickel-cadmium cell is installed in an energy-using device with built-in one-hour rate charging circuitry, the battery may be damaged by charging at a higher rate than it is capable of withstanding.
One object of this invention in one aspect thereof is to provide an energy-using device with built-in or associated charging circuitry, having the versatility to be powered by standard size batteries, both of the primary and rechargeable type, while recharging only rechargeable batteries which are compatible with the device (non-compatible rechargeable batteries may be recharged in an external, compatible charging device).
It is a further object in another aspect of the invention to provide an energy-using device with the versatility to be powered only by compatible rechargeable batteries designed for the energy-using device system, in respect to both discharge and charge of the batteries.
It is still a further object in another aspect to provide such an energy-using device having the characteristic of discriminating between rechargeable cells of differing rate capabilities, and enabling safe recharge of the batteries according to their particular rate capability.